Priority is claimed with respect to European Patent Application No. 00811089.2 filed in the European Patent Office on Nov. 17, 2000, the disclosure of which is incorporated herein by reference.
The invention relates to a spreader for spreading glue to the back or the adjoining areas of a book block of gathered printed pages, conveyed past the spreader on a conveyor. The glue spreader comprises a tub containing glue, into which at least one application roller that takes up the glue and transfers it to the book block is submerged. A blade coater, provided with an actuation element for adjusting the coater, is assigned to the application roller above the glue level in the tub. The blade coater determines the glue film thickness to be transferred to the back of the book block on the basis of the changeable distance to the application roller. The manner in which the glue is spread on the back of a book block is critical for a high-quality adhesive binding. Applying the glue with the aid of application rollers that can be adjusted, relative to the book back, favorably influences the quality of the adhesive bonding. The glue is frequently transferred with two successively arranged rollers and, in the process, minimal amounts are pushed mechanically between the page edges, so that the pages are embedded in the transferred glue.
The amount of glue to be applied is metered out with a controllable blade coater, among other things so that the glue cannot penetrate to the inside of the book. The height adjustment of the roller and the blade coater position must be carefully coordinated for this. Subsequently, the excess glue that is applied is leveled out with the aid of a vertically adjustable ductor blade or a leveling roller.
With known glue spreaders, the blade coaters are adjusted or set manually or via motor-driven cam disks, which act upon a control lever that is connected to the blade coater shaft. In addition, devices for which the blade coaters can be adjusted with the aid of adjustment motors that actuate a differential gear or a planetary gear are known. Also known are blade coaters operated with pneumatic cylinders, which are assigned an adjustable end stop.
The above mentioned known devices involve a relatively high design expenditure and require several elements to be effective. As a result, the adjustment accuracy suffers, especially due to existing or unavoidable play. Inaccuracies are unavoidable, even with the pneumatic actuation of a blade coater, since the speed for a pneumatic drive cannot be changed proportional to the machine speed.
It is an object of the invention to provide a glue spreader of the above-described type which permits an easy, exact and reliable adjustment of a blade coater.
The above and other objects are achieved according to the invention by the provision of a glue spreader for spreading glue to a back or adjacent area of a book block of gathered printed pages conveyed past the glue spreader on a conveyor, comprising: a tub for holding the glue; at least one application roller, adapted for being driven in the same direction and at the same speed as the book block, submerged in the tub for taking up the glue and transferring the glue to the back of the book block; a blade coater adapted for arrangement above the glue level in the tub at a changeable distance to the application roller; an actuation element coupled to the blade coater for adjustment of the blade coater for determining a thickness of a glue film to be transferred to the book block back based on the changeable distance to the application roller; and a controllable electric motor having a drive element, wherein the actuation element of the blade coater is operatively connected to the drive element of the controllable electric motor.
As a result of the invention, less space is required as compared to known embodiments. The actuation element for the blade coater is advantageously designed as a pivoting shaft, which makes it easy to establish a direct drive connection with an electric motor.
Owing to the fact that small masses must be accelerated, an electric motor designed as a linear motor is highly suitable for actuating a blade coater. Of course, a rotary electric motor can also be used for actuating the blade coater.
The invention is explained in the following with the aid of two exemplary embodiments and by referring to the drawing, which is referred to with respect to all details not explained further in the description.